Thermal history evaluation of low-grade altered or metamorphic rocks using thermometer based on geological kinetic indicator -estimation of duration of thermal event-

应用裂变退火动力学方法对松辽盆地进行了热史评价。首先，为确定白垩系地层的最大沉积年龄，对中央坳陷区、西翼地区及周边地区钻井采集的沉积岩进行了锆石和磷灰石裂变径迹定年及裂变径迹长度测量。白垩纪地层的锆石和磷灰石FT年龄和FT长度表明，源区在120-100 Ma有一个相当均匀的冷却历史。这说明盆地附近大兴安岭火山岩在沉积后不久即被剥蚀，并向松辽盆地方向改造。而盆地坳陷区深部岩芯中的磷灰石显示出严重的退火年龄。其次，为了估算白垩纪后的古地温，按以下步骤分析了各深度磷灰石的埋藏趋势。(1)让埋葬历史 关于我们 （2）假定古地温梯度为常数，（3）用正演模拟技术估算每个样品热历史的热重趋势，（4）预测的FT热重趋势与观测的FT热重趋势之间的统计检验。结果表明，较好的古地温值为40-45 ℃/km，古地温持续时间为几十万年。另一方面，分析了广泛的成熟度指标甲基菲指数（MPI），特别是在日本的绿色凝灰岩地区的油盆地，以了解MPI的变化及其与Ro %的关系。对于所有岩石样本，MPI显示在成熟区从0.7增加到4.2（%Ro=0.5-1.9），在过成熟区从4.2减少到1.3（%Ro=1.9-4.5）。用地球化学动力学方法讨论了这些趋势的上斜率，表明MPI的变化取决于中间MPI的产生和α-异构体向β-异构体的甲基转移。少

Thermal history evaluation using fission tack annealing kinetics was applied for the Songliao Basin. Firstly, to constrain the maximum deposition age of the Cretaceous Strata, zircon and apatite fission track dating and fission track length measurement have been carried out for the sedimentary rocks collected from the drilling well in the central depression area, western flank area and surrounding areas. Zircon and apatite FT ages and FT lengths for Cretaceous Strata suggest that the source region has a fairly homogeneous cooling history at 120-100 Ma. This means that the volcanic rocks in the Dahinganling Mountains near the basin were eroded soon after their deposition and were reworked toward the Songliao Basin. While, apatites from deep core sample at depression part of the basin show severely annealed ages. Secondary, to estimate post-Cretaceous paleo-geotherm, the younging trend of apatites from each depth were analyzed according to the following step. (1) Making burial history fo … More r each core sample using Sclater and Cristie's compaction model, (2) supposing the hypothetical constant paleo-geothermal gradients, (3) estimate younging trends for each sample's thermal histories using forward modeling technique, (4) statistical check between the predicted FT younging trend and observed younging trend. As a result, the good fitted paleo-geotherm was estimated for 40-45 ℃/km and several tens of Myrs was estimated for the duration of the geotherm. On the other hand, the methylphenanthrene index (MPI), wide-range maturation indicator, was analyzed especially from oil basin at green-tuff region in Japan to know the variation of MPI and its relation to Ro %. For all rock samples, the MPI showed increase from 0.7 to 4.2 in the mature zone (%Ro=0.5-1.9 and decrease from 4.2 to 1.3 in the over-mature zone %Ro=1.9-4.5. The upper slope in these trends was discussed by means of geochemical kinetics, suggesting that the MPI change depend on production of intermediate MPI and the methyl-shift from alpha-isomer to beta isomer. Less